Posterior vertebral support assembly

ABSTRACT

The invention concerns an assembly ( 1 ) comprising an interspinous wedge ( 5 ) configured to be inserted between the spinous processes ( 9 ) of two vertebrae ( 2 ) to be treated, whereof at least one zone designed to be placed between the spinous processes of the vertebrae is made of an elastically deformable material. The assembly ( 1 ) further comprises: two compressive lateral elements ( 6 ), designed to be placed on either side of the wedge ( 5 ) in the longitudinal direction, said compressive lateral elements ( 6 ) being deformable between releasing positions, wherein they are relatively spaced apart from the wedge ( 5 ) in the transverse direction, and compressive positions, wherein they are relatively close to the wedge ( 5 ) in the transverse direction; and two lateral transmission elements ( 7 ), placed between the compressive lateral elements ( 6 ) and the wedge ( 5 ), configured to press against the wedge ( 5 ) in the transverse direction thereof, at the interspinous zone ( 10 ) of the wedge ( 5 ).

This application is a national phase filing of international applicationno. PCT/FR2003/002635, filed Sep. 3, 2003, which claims priority toFrench patent application no. 02 11189, filed Sep. 10, 2002.

The present invention concerns a posterior vertebral support assembly.

In the case of degeneration of the intervertebral disc of two vertebraeand/or of ligament distension, it is known to place a wedge between thespinous processes of the two vertebrae concerned, making it possible tosupport the vertebrae. In this regard, reference may be made to FrenchPatent Applications Nos. FR 94 03716 and FR 98 02300 filed in the nameof the proprietor of the present application.

The wedges according to these earlier patent applications are connectedto the spinous processes of the two treated vertebrae by two independentligaments, each of the ligaments passing through the wedge and tightlysurrounding the corresponding spinous process. In the case of flexion ofthe spinal column in a forward direction, the spinous processes moveaway from one another, thereby causing longitudinal stretching of thewedge.

A drawback of this longitudinal stretching is that of stressing thewedge in longitudinal traction. The conditions of exertion of thistraction can however be perfected, in particular in order to obtainassisted and contained control of the movement of the vertebrae,inasmuch as the repetition of this traction threatens to affect thedurability of the wedge.

The present invention aims to remedy this drawback.

The assembly which it concerns comprises, in a manner known per se, aninterspinous wedge configured to be inserted between the spinousprocesses of two vertebrae to be treated, whereof at least the zonedesigned to be placed between the spinous processes of the vertebrae ismade of an elastically deformable material.

According to the invention, the assembly further comprises:

two compressive lateral elements, designed to be placed on either sideof the wedge in the longitudinal direction, the compressive lateralelements being deformable between releasing positions, which they occupywhen the vertebrae are in lordosis or when the spinal column isextended, and wherein they are relatively spaced apart from the wedge inthe transverse direction, and compressive positions, which they occupywhen the spinal column is in flexion, and wherein they are relativelyclose to the wedge in the transverse direction; and

two lateral transmission elements, placed between the compressivelateral elements and the wedge, configured in order, when thecompressive lateral elements are displaced in said compressive position,to press against the wedge in the transverse direction thereof, at thezone of the wedge designed to be placed between the spinous processes ofthe vertebrae.

The assembly according to the invention thus makes it possible to exerta progressive transverse compression on the wedge during the movement offlexion of the spinal column. This compression will reduce the shearstresses which are exerted on the wedge during intervertebral distancingcombining tilting and forward sliding movements, owing to thecontainment of the displacements effected by the wedge.

The transverse compression of the wedge is preferable to purelongitudinal traction from the point of view of durability of the wedge,since it compensates the stressing of the wedge in the longitudinaldirection.

The zone of the wedge designed to be placed between the spinousprocesses may be made of a material having limit of compressibility inthe transverse direction of the wedge, and the assembly may then beconfigured such that this limit is reached when the treated vertebraeattain a predetermined tilted position.

It is also possible to configure the compressive lateral elements sothat the elements have a limit of deformation in the transversedirection, this limit of deformation being reached when the treatedvertebrae attain a predetermined tilted position.

The compressive lateral elements may be deformed nonelastically orelastically between said releasing and compressive positions. In thelatter case, the return force of the elements to their neutral formcontributes to the damping of the tilting movement of the treatedvertebrae.

The compressive lateral elements may likewise be elastically deformablein the longitudinal direction of the compressive lateral elements, tothe same end.

According to one embodiment of the invention, the compressive lateralelements are independent of one another, and each is connected to one ofthe treated vertebrae by one end and to the other treated vertebra byits other end. The connection of the ends of the compressive lateralelements to the vertebrae may in particular be effected at the pediclesof the vertebrae, by means of pedicular screws engaged in eyelets oranchorage pieces included in the compressive lateral elements.

The connection of the compressive lateral elements to the vertebrae mayalso be effected, in the case of the overlying vertebra, by means of thepassage of the elements beneath the laminae of that vertebra. Thissub-laminal passage makes it possible to preserve the pedicles and to beas central as possible in order, during the longitudinal elongation, tooptimize the transverse thrust exerted on the wedge. In the case of theunderlying vertebra, these same compressive lateral elements may also beconnected to an interpedicular transverse connecting bar, placed inposition especially in the case of laminectomy on this vertebra, thusmaking it possible to reduce the concentration of strains. Similarly,the compressive lateral elements may be connected to a connecting barjoined to a system of arthrodesis of the two underlying vertebrae.

According to another embodiment of the invention, the compressivelateral elements are formed by the two lateral portions of a circularstrap engaged round the spinous processes of the two treated vertebrae.

The lateral transmission elements themselves may be constituted by smallbars bearing on the one hand against the compressive lateral elementsand on the other hand against the wedge, especially via small supportplates.

These same lateral transmission elements may likewise be constituted bybosses connected either to the compressive lateral elements or to thewedge. In the latter case, the bosses may be integral with the wedge.

The wedge may be made entirely of an elastically deformable materialsuch as a silicone; it may in particular comprise a core made of such amaterial and a textile envelope containing the core.

The wedge may also be formed by a band of resilient material, suitablycurved.

The wedge may comprise a spring placed transversely at its zone designedto be placed between the spinous processes.

For greater understanding thereof, the invention is described againhereinafter with reference to the appended diagrammatic drawingrepresenting, by way of non-limiting example, several possibleembodiments of the assembly concerned.

FIG. 1 is a rear view, very simplified, after the positioning on twovertebrae;

FIG. 2 is a view similar to FIG. 1, according to the second embodiment;

FIG. 3 is a view similar to FIG. 1, according to the third embodiment,only the spinous processes of the vertebrae being shown, and

FIG. 4 is a view similar to FIG. 3, according to a variant.

FIG. 1 represents a posterior vertebral support assembly 1 placed inposition on two vertebrae 2 affected by degeneration of the disc 3and/or ligament distension.

The assembly 1 comprises an interspinous wedge 5, two compressivelateral elements 6 and two lateral transmission elements 7.

The wedge 5 is made of an elastically flexible material and comprisestwo curved recesses 8 allowing it to be inserted between the spinousprocesses 9 of the two vertebrae 2. It may in particular conform to thewedge according to French Patent Application No. FR 98 02300, that is tosay:

comprising a core made of silicone and an envelope made of polyesterfabric,

having an interspinous portion 10 having a height greater than thedistance separating the spinous processes 9 when the vertebrae 2 are inlordosis in order to be compressed when the wedge 5 is inserted betweenthe processes 9 and to permit relief of the disc 3 and also restorationof the ligaments to functional tension, and

having lugs 11 which bound the curved recesses 8, the lugs 11 broadlyenveloping the processes 9 and being self-tightened round the processes9 when said interspinous portion 10 is compressed.

The wedge 5 shown in FIG. 1 differs, however, from the wedge accordingto the aforesaid French Patent Application No. FR 98 02300 in that ithas domed lateral walls, imparting to it a relatively large width atsaid interspinous portion 10.

Each element 6 is formed by a lamina 15 made of elastically deformablesynthetic material and by two eyelets 16 connected to the ends of thelamina 15. The latter is curved and comprises the element 7 at themedian portion of its concave face, the concave face being designed tobe turned towards the wedge 5.

The eyelets 16 are designed to receive pedicular screws permitting theanchorage of the elements 6 to the vertebrae 2.

Each element 7 is formed by a small rigid bar 20 fixed to an element 6,and is oriented substantially perpendicularly to the zone of the element6 to which it is connected. The bar 20 is placed, after implantation, atthe interspinous portion 10 of the wedge 5.

Each bar 20 is rigidly connected with a small plate 21 for bearingagainst the portion 10.

The assembly 1 according to the invention is in the position shown inFIG. 1 when the vertebrae 2 are in lordosis.

In the case of extension of the spinal column, the vertebrae 2 pivot ina direction in which the processes 9 are brought closer to one another,thereby leading to compression of the wedge 5 up to the limit ofelasticity of the material constituting the core of the wedge. A dampingof the pivoting movement of the vertebrae 2 is thus obtained as long assaid limit of elasticity is not reached, then the arresting of that samemovement is obtained when the limit of elasticity is reached. Duringthis compression of the wedge 5, the elements 6 are deformed in thedirection in which their curvature is increased, contributing to thedamping of the movement of the vertebrae 2. The elements 6 likewiseprovide a perfect guarantee of maintenance of the position of the wedge5 between the processes 9.

In the case of flexure of the spinal column, the vertebrae 2 pivot in adirection in which the processes 9 are spaced from each other, therebyleading to a reduction in the curvature of the elements 6. The elements7 then press against the wedge 5 transversely, thereby also making itpossible to dampen the movement of the vertebrae 2 then to arrest thatmovement when the limit of elasticity of the material forming the coreof the wedge 5 is reached and/or when the elements come close to asubstantially rectilinear form.

FIG. 2 shows an assembly 1 similar to that just described, except thatthe elements 6 are formed by the two lateral portions of a circularstrap 25 engaged round the processes 9 of the vertebrae 2. The otherportions or elements already described, which are to be found again inthis second embodiment, are not described again and are designated bythe same numerical references as before.

The strap 25 may be made of a slightly elastically stretchable material,and thus also contributes to the damping and then blocking of thepivoting movement of the vertebrae 2 in the case of flexion of thespinal column.

FIGS. 3 and 4 show a third embodiment of the assembly 1, in which thelatter is similar to that shown in FIG. 2, except that the small bars 20and plates 21 are replaced by bosses 30 along which pass the lateralportions of the strap 25. The bosses 30 may be fixed to the wedge 5 orbe integral therewith, as shown in FIG. 3, or may be rigidly connectedwith the strap 25 and bear against the wedge 5, optionally at lateralrecesses which the wedge includes to receive them, as shown in FIG. 4.

As it appears from the foregoing, the invention provides a decisiveimprovement on the prior art, by providing a posterior vertebral supportassembly which does not stress the wedge in the longitudinal directionduring the movement of flexion of the spinal column. Perfect control ofthe movement of the vertebrae is obtained by means of this assembly, andthe durability of the wedge is not affected by the repeated movements ofthe vertebrae.

It is self-evident that the invention is not limited to the embodimentdescribed above by way of example, but that on the contrary itencompasses all the variants of embodiment coming within the scope ofprotection defined by the appended claims.

1. A posterior vertebral support assembly (1), comprising aninterspinous wedge (5) configured to be inserted between the spinousprocesses (9) of two vertebrae (2) to be treated, whereof at least thezone designed to be placed between the spinous processes of thevertebrae is made of an elastically deformable material; an assembly (1)characterized in that it comprises: two compressive lateral elements(6), designed to be placed on either side of the wedge (5) in thelongitudinal direction, the compressive lateral elements (6) beingdeformable between releasing positions, which they occupy when thevertebrae (2) are in lordosis or when the spinal column is extended, andwherein they are relatively spaced apart from the wedge (5) in thetransverse direction, and compressive positions, which they occupy whenthe spinal column is in flexion, and wherein they are relatively closeto the wedge (5) in the transverse direction; and two lateraltransmission elements (7), placed between the compressive lateralelements (6) and the wedge (5), configured in order, when thecompressive lateral elements (6) are displaced in said compressiveposition, to press against the wedge (5) in the transverse directionthereof, at the zone (10) of the wedge (5) designed to be placed betweenthe spinous processes (9) of the vertebrae (2).
 2. A support assembly(1) according to claim 1, characterized in that the materialconstituting the zone of the wedge (5) designed to be placed between thespinous processes has a limit of compressibility in the transversedirection of the wedge (5), and in that the assembly (1) is configuredsuch that this limit is reached when the treated vertebrae (2) attain apredetermined tilted position.
 3. A support assembly (1) according toclaim 1, characterized in that the compressive lateral elements (6) areconfigured so as to have a limit of deformation in the transversedirection, this limit of deformation being reached when the treatedvertebrae (2) attain a predetermined tilted position.
 4. A supportassembly (1) according to claim 1, characterized in that the compressivelateral elements (6) are configured so as to be elastically deformablebetween said releasing and compressive positions.
 5. A support assembly(1) according to claim 1, characterized in that the compressive lateralelements (6) are configured so as to be elastically deformable in thelongitudinal direction of the compressive lateral elements (6).
 6. Asupport assembly (1) according to claim 1, characterised in that thecompressive lateral elements (6) are independent of one another, and inthat each is connected to one of the treated vertebrae (2) by one endand to the other treated vertebra (2) by its other end.
 7. A supportassembly (1) according to claim 6, characterised in that the compressivelateral elements (6) comprise eyelets (16) or anchorage pieces designedto receive pedicular anchorage screws for anchoring the compressivelateral elements (6) to the vertebrae (2).
 8. A support assembly (1)according to claim 1, characterized in that the compressive lateralelements are configured so as to be able to pass beneath the laminae ofthe overlying vertebra.
 9. A support assembly (1) according to claim 1,characterized in that the compressive lateral elements are configured soas to be able to be connected to an interpedicular transverse connectingbar, placed in position on the underlying vertebra especially in thecase of laminectomy.
 10. A support assembly (1) according to claim 1,characterized in that the compressive lateral elements are configured soas to be able to be connected to a connecting bar joined to a system ofarthrodesis of the two underlying vertebrae.
 11. A support assembly (1)according to claim 1, characterized in that the compressive lateralelements (6) are formed by the two lateral portions of a circular strap(25) engaged round the spinous processes (9) of the two treatedvertebrae (2).
 12. A support assembly (1) according to claim 1,characterized in that the lateral transmission elements (7) areconstituted by small bars (2) bearing on the one hand against thecompressive lateral elements (6) and on the other hand against the wedge(5).
 13. A support assembly (1) according to claim 1, characterized inthat the lateral transmission elements (7) are constituted by bosses(30) connected either to the compressive lateral elements (6) or to thewedge (5).